A Study of HLX18 vs. OPDIVO® in Multiple Resected Solid Tumors

Inclusion criteria

• Participants must have signed and dated an IRB/IEC approved written informed consent form.
• Aged 18 to 70 years at the time of signing the ICF.
• 18 kg/m² ≤ BMI ≤ 30 kg/m² and 50 kg ≤ body weight ≤ 85 kg.
• Histologically confirmed solid tumors (EC/GEJC, Melanoma, or UC) status post R0 resection.
• For EC/GEJC: residual pathologic disease (non-pCR) following neoadjuvant chemoradiotherapy and R0 resection.
• For Melanoma: Stage IIB-IV after complete surgical resection with documented negative margins.
• For UC: High-risk muscle-invasive urothelial carcinoma (MIUC) following radical resection (R0).
• Documented disease-free status (no recurrence) by imaging and physical exam within 4 weeks prior to randomization.
• Adequate recovery from prior surgery or systemic therapy.
• ECOG Performance Status of 0.
• Adequate organ function.
• Agreement to use effective contraception (negative pregnancy test for WOCBP).

Exclusion criteria

• History of illicit drug use or alcohol abuse within 12 months prior to randomization.
• Tumor-specific exclusions: cervical esophageal cancer, Stage IV EC/GEJC, or ocular melanoma.
• UC-specific surgical exclusions: status post partial cystectomy or partial nephrectomy.
• EC/GEJC treatment violations: failure to receive mandatory preoperative concurrent CRT (mono-therapy is ineligible).
• Prior treatment with nivolumab or any other immune checkpoint inhibitors (PD-1, PD-L1, CTLA-4).
• Other primary active malignancies within 5 years or history of organ/bone marrow transplantation.
• Significant cardiovascular disease (MI, cerebrovascular disease) or unstable arrhythmia (QTc \> 450ms/470ms) within 6 months.
• Chronic heart failure (NYHA Class III-IV) or LVEF \< 50% at screening.
• Presence of interstitial pneumonia, pneumonitis, or severe lung function abnormalities.
• Active autoimmune disease requiring systemic immunosuppressive therapy.
• Known HIV infection, active Hepatitis B/C, or active pulmonary tuberculosis.
• Peripheral neuropathy ≥ Grade 2 or history of carcinomatosis meningitis.
• Use of systemic corticosteroids (\>10 mg/day prednisone equivalent), immunosuppressants, or live vaccines within 28 days.
• Recent or planned participation in other investigational drug, device, or surgical studies.
• Severe allergic reactions to monoclonal antibodies or any condition deemed unsuitable by the investigator.
• The investigator has a clear reason to believe that participation in this study would be detrimental to the participant.